Comparison of lateral surgical margins of up to two centimeters with margins of three centimeters for achieving tumor-free histologic margins following excision of grade I or II cutaneous mast cell tumors in dogs

Abstract

OBJECTIVE To determine whether conservative lateral surgical margins (equal to tumor diameter for tumors < 2 cm in diameter or 2 cm for larger tumors) were noninferior to wide (3-cm) lateral surgical margins for achieving tumor-free histologic margins following excision of grade I and II cutaneous mast cell tumors (MCTs) in dogs. ANIMALS 83 grade I and II MCTs excised with a deep surgical fascial margin and requisite lateral surgical margins from 68 dogs from 2007 to 2017. Tumors representing scar revision or local recurrence were excluded. PROCEDURES A pathology department database was searched to identify qualifying MCTs, and medical records were cross-referenced to obtain data regarding patients and tumors. Outcome (complete vs incomplete excision as histologically determined) was compared between conservative- and wide-margin groups. A noninferiority margin of ≥ 0.9 was used for the risk ratio (probability of complete excision for the conservative- vs wide-margin group), implying that noninferiority would be established if the data indicated that the true risk of complete excision with the conservative-margin approach was at worst 90% of that for the wide-margin approach. RESULTS The proportion of excised MCTs with tumor-free histologic margins was similar between the conservative- (43/46 [93%]) and wide- (34/37 [92%]) margin groups. There were no differences in tumor diameter or location between treatment groups. The risk ratio (1.02; 95% confidence interval, 0.89 to 1.19) met the criterion for noninferiority. CONCLUSIONS AND CLINICAL RELEVANCE The conservative-margin approach appeared to be noninferior to the wide-margin approach for achieving tumor-free histologic margins in the dogs of this study, and its use could potentially reduce the risk of postoperative complications. (J Am Vet Med Assoc 2020;256:567-572

Influence of locoregional lymph node aspiration cytology vs sentinel lymph node mapping and biopsy on disease stage assignment in dogs with integumentary mast cell tumors

“…Curative intent surgical excision was performed while dogs were under general anesthesia by board‐certified surgeons for all MCT. En bloc excision was performed with proportional lateral margins for MCT >1 cm but ≤2 cm in diameter and with 3‐cm lateral margins for MCT >2 cm in diameter 16 . A deep margin of one fascial plane was taken for all tumors.…”

“…En bloc excision was performed with proportional lateral margins for MCT >1 cm but ≤2 cm in diameter and with 3-cm lateral margins for MCT >2 cm in diameter. 16 A deep margin of one fascial plane was taken for all tumors. All dogs received appropriate analgesic protocols for their procedures as determined by a board-certified anesthesiologist and/or surgeon, consisting of opioid analgesia and epidural blockade/transversus abdominis plane blockade/splash blocks as appropriate.…”

Long-term postsurgical outcomes of mast cell tumors resected with a margin proportional to the tumor diameter in 23 dogs

“…One potential disadvantage of PM resection is an increased risk of incomplete MCT excision, which is of particular concern for high grade MCTs [2]. It should be noted that all MCTs managed by PM resection in the present study were Kiupel's low grade MCTs.…”

“…Complete resection with a wide margin of normal tissue is widely accepted as the best treatment for localized MCTs [1,9]. Recently, it has been recognized that the traditional 3-cm lateral margin is not always required; a 2-cm lateral margin with one fascial plane being sufficient when resecting most grade 1−2 MCTs [2,4,17]. However, the optimal margin for grade 3 MCT has not been well investigated [15].…”

“…Potential benefits of PM resection include minimal invasiveness [2,15], feasibility in sites where wide margins cannot be achieved for anatomical reasons [15], and applicability regardless of histologic site (cutaneous or subcutaneous) and grade [15]. Six of the original MCTs in six dogs were excluded from our study because the margins were too large or too small; we were able to perform PM resection on the remaining 33 of 39 MCTs (85%) that were resected during the study period ( Fig.…”